Synthetic fibers, yarns and fabrics are often subjected to heat-setting processes during manufacture so as to confer dimensional stability and other desirable properties to the finished synthetic fiber product. One well known technique is the Suessen heat-setting process which involves wrapping synthetic fibers or yarns around a moveable support frame comprised of elongate heat-resistant support cords (e.g., formed of polyaramid fibers, such as Nomex-brand fibers). The support cords forming the moveable frame thus support the synthetic fibers or yarns in a relative "open" condition where substantially no contact occurs between adjacent turns of the fibers or yarns wrapped about the support cords. Controlled conveyance through a heat-setting oven therefore imparts the desired heat-set properties to the fibers or yarns.
One problem associated with the Suessen heat-setting process is that, since the fibers are wrapped around heat-resistant support cords, some differential heat-setting conditions will be realized particularly where the fibers being heat-set come into physical contact with the support cord. Variations in yarn tension may also be present. This differential heat-setting thereby results in differential dying, coloration or crimp development of the fibers thereby causing visually perceptible color differences (known in art parlance as "chevrons") to be discernable in the finished fabric product. Using commercial scale Suessen heat-setting equipment to investigate heat-setting conditions for various synthetic fibers that may give rise to imperfections (chevrons) in the finished fabric product so that such conditions may be avoided is clearly not economically viable.
Therefore, what has been needed is a laboratory scale device which, when employed in conjunction with a laboratory scale heat-setting oven, may assist investigators in simulating heat-setting conditions so that imperfections (chevrons) in the finished fiber product may be minimized or eliminated entirely when operated on a commercial scale. It is towards providing such a device that the present invention is directed.
Broadly, therefore, the present invention is embodied in a laboratory scale device which may be used in cooperation with a laboratory scale heat-setting oven so as to simulate Suessen heat-setting conditions. In preferred forms, the present invention is embodied in a laboratory-scale device for assisting in the simulation of heat setting conditions which includes a pair of laterally spaced-apart flexible heat-resistant cords tensioned between forward and rearward rigid cross-support bars. At least one rigid tensioning bar is provided parallel to the support cords and extending between the cross-support bars so as to maintain the desired tension on the flexible heat-resistant cords. The tensioning bar thus allows for manual or automated lateral winding of the synthetic heat-settable fibers or yarns about the spaced-apart heat-resistant cords during preparation of the device for a test run. The tensioning bar may thereafter be removed once the device has been secured in position with the laboratory heat-setting oven. In such a manner, therefore, various effects on heat-setting conditions simulating the Suessen heat-setting process can be investigated without resorting to the use of full scale commercial heat-setting equipment and the resulting idled production from such use.
Further aspects and advantages will become more clear after careful consideration is given to the following detailed description of the preferred exemplary embodiments thereof.